Magnetic teletypewriter transmittal distributor head



Nov. 12, 1963 1 K. A. H. SMITH MAGNETIC TELETYPEWRITER TRANSMITTAL DISTRIBUTOR HEAD 2 Sheets-Sheet 1 Filed Sept. 27, 1957 INVENTOR KENNETH A.H. SMITH ATTORNEYS Nov. 12, 1963 K. A. H. SMITH 3,110,767

MAGNETIC TELETYPEWRITER TRANSMITTAL DISTRIBUTOR HEAD Filed Sept. 27, 1957 2 Sheets-Sheet 2 (MHVW) dOlS AD 1 WW GJVHSJIHVJS INVENTOR KENNETH AH. SMITH STOP v LMARK) 6. 44-20 A ORNEY$ United States Patent Ofifice 'ii llii 'ifi'i Patented Nov. 12, 1963 (Granted under Title 35, Code The invention described herein may be manufactured and used by and for the Government of the United States of America for governmental purposes without the payment or" any royalties thereon or therefor.

"ihis invention relates to a magnetic teletypwriter trans mittal distributor head using a rotatable permanent magnet, a number of pick-up coils spaced around the periphery of the travel of the permanent magnet, and a rectitying means consisting of a diode for shaping the output pulse so that a precisely timed teletypewriter signal is obtained.

In the past a number of distributor heads for teletypewriter machines have been made which usually consist of a rotating, electrical contact or commutator with brushes.

Commutator type distributor heads consist of a brush and a number of commutator segments which make and break an electrical circuit which is usually highly inductive in character. When any electrical circuit is broken, and particularly a highly inductive one, arcing occurs and some electromagnetic waves are generated. With sensitive instruments, these waves can be detected at considerable distances from the commutator despite elaborate shield-rig cf the commutator.

This radiation seriously jeopardizes the security of a classified communication or crytographic system which otherwise could be considered completely secret.

A primary object of this invention is therefore to provide a teletypewriter transmittal distributor h ad which does not generate any appreciable electromagnetic radiation.

In addition, the commutator type distributor brushes bounce and thereby create an ambiguity at the beginning and end of the output pulse. Capacitor and induction type distributors have been suggested to eliminate brush wear and bounce of the commutator type, but they are unsuitable in many applications since a precisely timed output pulse is diihcult to generate and these distributors require expensive amplifying and shaping circuits.

in the present invention a rotating permanent magnet, which is synchronized with teletypewriter motor shaft, sweeps past a number of induction coils which generate an alternating voltage in response to the passage or" the permanent magnet. A diode rectifier is used in the circuit of the induction coil to rectify the alternating voltage from the coil and thereby pass a pulse which has a sharp leading edge, precisely positioned within each cycle, which does not vary with the wear and tear in the machine.

Another object of this invention is therefore to provide a teletypewrlter transmittal distributor head which uses no movable contacts and which will not wear out within any reasonable time. A further object of this invention is to utilize a rectifying circuit in conjunction with the distributor head whereby a precisely timed output will be obtained from the distributor head, thereby eliminating any ambiguity of timing or jitter in the output pulse.

Gther objects and advantages of the invention will hereinafter become more fully apparent from the following description of the annexed drawings, which illustrate a preferred embodiment, and wherein:

E6. 1 is a plan view of a preferred embodiment of the invention;

FIG. 2 is a schematic diagram of the magnetic distributor head and associated circuitry;

Start, numbers PEG. 3 shows the typical wave forms encountered in the circuit of 2.

Referring to PEG. 1, a teletypewriter transmittal distributor head is shown at it and a frame or support 12 is shown for mounting the various parts.

A number of pick-up coils 14 are shown spaced around the periphery of the frame These are indicated as a, 2, 3, l, 5 and Stop, corresponding to the conventional teietypewriter code. A coil core 16 is shown projecting sli ly from the axis of the pick-up coils order to generate a precisely timed output pulse from the pic -up coils i l, permanent magnet 20 having a north pole and a south pole as shown is rotatably mounted in the center of the head. A split shaft 22 which enables the magne to be clam-"Jed by means of a fastener 24 is as shown. The split s aft 22- is adapted to be driven by a teietypewriter transm' tal distributor motor shaft connected to a teletypewriter machine (not shown).

A number of diodes marked 26 for shaping the output of the pick-up coils Ir are shown mounted next to the pick-up coils A common line 28 for the diodes is shown onuected to out =t resistors and The irame is greierably made of a magnetic material such as steel in order to cor :lete the magnetic circuit from the unanent ma t 23, through the induction coils i4, and rough the steel .te to the central shaft which grips the south end or the permanent magnet. In addition soft steel cover (not shown) may be used in order to eliminate any information bearing magnetic radiation to keep dust and iron particles out of the distributor lap did.

2, a schematic diagram of the ape pick-up coils 14 are marked The diodes are indicated as nurnbes 39 through 45. The output of the pick-up coils id is fed to a positive output line 43 or a negative output line 56. This connection is either permanent as in the case of the Stop and Start coils or may be made by means of switches 55 which are operated by the teietypewriter machine in response to the proper code which is to be sent out. The positive line 48 and negative line it iced two resistors and 3-2 and a transformer 34 o is shown having a primary 3.? and a secondary 38. common line of the diodes is returned to the midpoint of the resistors 3'? and and may be grounded at 64 if desired.

Referring to FIG. 3 the wave forms of the circuit which 2 exhibits are as shown. The normal output from a pick-up coil 14 when the permanent magnet 2i} passes next to its core is shown at and 6%. It will be noted that this wave form is of an alternating type for it increases at and then decreases rapidly to a negative value and then back to O as shown at 63. The function oi diodes to is to act to cut oil the positive part e wave form shown in PEG. 3 and to pass the negative portion marked it will be seen that this Wave form 69 has a sharp leading edge with a sloping trailing edge.

Wave forms 53 and 6% are due to the increase of magnetic flux in the coil as the magnet 213' approaches the coil and the decrease in flux in the coils as the magnet moves away from the coils, thereby inducing an alternating voltage in the coil. This point at which the voltage in the coil changes polari y is almost exactly at the mechanical center of the coil core, 16, which allows the coils to be positioned at a particular point to insure the precise determination of the beginning of the negative pulse 6%.

The precise time at which pulse 6 3 begins is therefore dependent upon the mechanical structure of the distributor "(la i:

3 head and normally will not vary except with the speed of rotation of the magnet 20, which speed is predetermined by the requirements of the teletypewriter communication system. a

The outputfrom the transformer 34 is shown at 62 corresponding to the placement of the switches as shown in FIG. 2. The transformer 34 acts to reverse the pulses connected to the space bar or negative line 50 and therefore the desired pulse output is obtained.

The output 62 as shown in FIG. 3 may then be fed to suitable square wave, pulse generating circuits to generate the desired pulses which are used in a teletypewriter system.

The use of the diodes 39-45 allows 'a sharp output pulse to be generated which is particularly suitable for generating a teletypewriter signal which will not vary with time or suffer from jitter.

An example of the circuit values in a preferred embodiment of the invention are as follows:

Permanent magnet 20Alnico V alloy, A" diameter,

2 in length Core 16a soft magnetic material, x V!" x Coils 14-2000 turns of #38 AWG Diodes 26-type 1N34 Resistor A=B=50OSZ Average output voltage of coils 14 underload and with magnet 20 rotating at an average teletypewriter speed of 300 r.p.m.-1 volt It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that it is intended to cover all changes and modifications of the example of the invention herein chosen for the purposes of the disclosure, which do not constitute departures from the spirit and scope of the invention.

What is claimed is:

1. A magnetic teletypewriter transmittal distributor head for teletypewriter machines comprising a rotatably mounted permanent magnet with a first pole of the magnet having a chisel point and placed radially from the center of rotation of said magnet and with a second pole of said magnet placed radially inward toward the center of rotation of said magnet from said first pole, said magnet adapted to be synchronized with a teletype machine, seven electromagnetic coils placed next to the radius of rotation of said first pole of said magnet, each coil comprising a core having a portion thereof adjacent said radius and a winding mounted on said core responsive to the passage of said magnet to generate an alternating output, seven diodes wherein a diode is connected to the output of each one of said windings whereby the alternating output is rectified allowing a unidirectional signal to be obtained from each winding whereby a precisely determined output pulse sequence is obtained, positive and negative output lines for combining the output of said windings, switching means connected between the output of said windings and said positive and negative output lines responsive to a teletypewriter code, and transformer means for combining the output on said negative and positive output lines whereby a space signal will be obtained for a negative signal and a mark signal obtained for a positive signal.

2. A magnetic teletypewriter transmittal distributor head for teletypewriter machines comprising a rotatably mounted permanent magnet with a first pole of the magnet having a chisel point and placed radially from the center of rotation of said magnet and with :a second pole of said magnet placed radially inward toward the center of rotation of said magnet from said first pole, a plurality of electro-magnetic coils placed next to the radius of rotation of said first pole of said magnet, each coil comprising a core having a portion thereof adjacent said radius and a winding mounted on each said core responsive to the a diode connected to the output of each one of said windings whereby the alternating output is rectified allowing a unidirectional signal to be obtained from each winding whereby a predetermined output pulse sequence is obtained; positive and negative output lines for combining the outputs of said windings, switching means connected between the outputs of said windings and said positive and negative output lines responsive to a teletypewriter code, and transformer means for combining the output on said positive and negative output lines whereby a space signal will be obtained for a negative signal and a mark signal obtained for the positive signal.

3. A magnetic transmittal distributor head for teletypewriter machines comprising a rotatably mounted permanent magnet having a first pole placed radially from the center of rotation of said magnet and a second pole placed radially inward toward the center of rotation of said magnet from said first pole, said magnet adapted to be rotated in synchronization with said teletypewriter machine, a plurality of electromagnetic coils placed next to the radius of rotation of said first pole of said magnet, whereby said coils generate an alternating output in response to the passage of said magnet, rectifier means connected to the output of each of said electromagnetic coils to provide a unidirectional signal, whereby a precisely determined output pulse sequence is obtained; positive and negative output lines for combining the outputs of said coils, switching means connected between the output of said coils and said'positive and negative output lines, said switching means being responsive to a predetermined code, and means for combining the output on said negative and positive output lines whereby a space signal will be obtained for a negative signal and a mark signal obtained for a positive signal.

4. A magnetic transmittal distributor head for teletypewriter machines comprising a rotatably mounted permanent magnet having a first pole placed radially from the center of rotation of said magnet and a second pole placed radially inwardly toward the center of rotation of said magnet from said first pole, a plurality of electromagnetic coils placed next to the radius of rotation of said first pole of said magnet, whereby an output is generated in said coils by the passage of said magnet pole, rectifier means connected to the output of each of said 'coils thereby providing a unidirectional signal from each of said coils, positive and negative output lines combining the output of said coils, and switching means connected between the output of said coils and said positive and negative output lines responsive to a teletypewriter code.

References Cited in the file of this patent UNITED STATES PATENTS 1,844,950 Finch Feb. 16, 1932 2,356,221 Cox Aug. 22, 1944 2,401,175 Morrill May 28, 1946 2,430,379 Wall Nov. 4, 1947 2,659,866 Landon Nov. 17, 1953 2,734,942 Heald Feb. 14, 1956 2,740,110 Trimole Mar. 27, 1956 2,786,182 Herbert Mar. 19, 1957 2,807,756 Cronin Sept. 24, 1957 2,866,869 S-inninger Dec. 30, 1958 FOREIGN PATENTS 7 952,196 Germany Nov. 15, 1956 OTHER REFERENCES Publication: Electric Machinery (textbook), by Fitzgerald and Kingsley; published by McGnaw-Hill (1952), Library of Congress, card no. 5 1-12939, pages 19 and 23.

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4. A MAGNETIC TRANSMITTAL DISTRIBUTOR HEAD FOR TELETYPEWRITER MACHINES COMPRISING A ROTATABLY MOUNTED PERMANENT MAGNET HAVING A FIRST POLE PLACED RADIALLY FROM THE CENTER OF ROTATION OF SAID MAGNET AND A SECOND POLE PLACED RADIALLY INWARDLY TOWARD THE CENTER OF ROTATION OF SAID MAGNET FROM SAID FIRST POLE, A PLURALITY OF ELECTROMAGNETIC COILS PLACED NEXT TO THE RADIUS OF ROTATION OF SAID FIRST POLE OF SAID MAGNET, WHEREBY AN OUTPUT IS GENERATED IN SAID COILS BY THE PASSAGE OF SAID MAGNET POLE, RECTIFIER MEANS CONNECTED TO THE OUTPUT OF EACH OF SAID COILS THEREBY PROVIDING A UNIDIRECTIONAL SIGNAL FROM EACH OF SAID COILS, POSITIVE AND NEGATIVE OUTPUT LINES COMBINING THE OUTPUT OF SAID COILS, AND SWITCHING MEANS CONNECTED 